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14.1 Earth History

Fossils and Geologic Time Scale

When Earth Formed... billion years ago 4.6 billion years ago
Briefly describe features of the Early Earth Molten with volcanic features
Briefly describe the Early Atmosphere... What was missing? similar to gases expelled by volcanoes.... Little or no free oxygen
When were the earliest fossils ? Earlier evidence of life was found in chemical markings... when were these chemical markings 3.5 bya 3.8 bya
Preserved evidence of organisms Fossils
Discuss the Fossil Record Analogy It is like a book with many missing pages .. are still filling in the gaps
What word can describe the percentage of organisms preserved as fossils ( hint: all, most, tiny amount) tiny amount
What happens to most organisms before they have a chance to become fossilized? they decay
what situation provides the most fossils? organisms buried rapidly in sediment... most frequently in a watery environment
What word describes a fossil that is an impression of the organism MOLD
How is the fossil called a CAST different from the fossil called a MOLD the cast is filled in with sediment
Footprints, burrows and fossilized feces provide indirect evidence of organisms ...they are called trace fossils
How does petrified wood form ? empty areas were filled in with minerals. ( may happen in a swampy area where trees become submerged)
Preserved Tree sap that may trap and entire organism ( many insects are in this substance) Amber
Two things that preserve the original organisms Mummification and freezing
Fossils are more common in ______rock? Why? Sedimentary ... fossils usually don't survive the heat or pressure needed to form igneous or metamorphic rock
The record of Earth's history with major geological and biological events Geologic Time Scale
mya or bya millions of years ago , billions of years ago
Nearly 90% of the earth's entire history ( first 4 billion years) Earth formed, First life, autotrophic prokaryotes enriched atmosphere with oxygen, eukaryotic cells began... and others Precambrian Time ( supereon)
Major changes in Ocean Life, First Life on Land, Swampy Forests( produced much of our coal), Huge insects, tetrapods, first reptiles Paleozoic era
Who were the first land vertebrates... When did they appear Tetrapods, Paleozoic era
What often marks the boundary between the eras etc.. mass extinctions
Era that had dinosaurs as the dominant organisms... also had early mammals, flowering plants and birds Mesozoic era
What is a common hypothesis to explain the extinction of dinosaurs... .When did this occur meteorite, 65 mya
Primary evidence for meteorite impact that caused the dinosaur extinction.. this has high levels of iridium which is rare on earth but common in meteorites.. iridium common on Mars KT Boundary.. between rocks of mesozoic era and Cenozoic era
the most recent era when mammals became dominant land animal Cenozoic
What was true about the first mammals ( hint: size, animal they resemble) they were small and resembled shrews(mouse)
Created by: shemehl



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